Means for controlling casting



Feb. 4, 1969 R. J. D-EAR-TH 3 .5

MEANS FOR CONTROLLING CASTING Filed May 13, 1966 Ra y/none! J Dee if? United States Patent 3,425,483 I MEANS FOR CONTROLLING CASTING Raymond J. Dearth, Roselle, Ill., assignor to Amsted Industries Incorporated, Chicago, Ill., a corporation of New Jersey Continuation-impart of application Ser. No. 298,130, July 29, 1963. This application May 13, 1966, Ser. No. 554,278 US. Cl. 164-155 Int. Cl. B22c 19/04; B22d 17/32 7 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to pressure casting and is a continuation-in-part of applicants application, Ser. No. 298,130, filed July 29, 1965, now abandoned.

The invention relates more particularly to means for and method of controlling the rate of pouring in a casting operation.

Molten metal varies as between casting operations; for example, different batches will vary from one to another and it may vary in one batch as circumstances change; such variations include change in viscosity which affects the rate of pouring.

A broad object of the invention is to provide means for and method of automatically controlling the rate of pouring the molten metal in the casting operation by sensing differential in air pressure applied to the molten metal and controlling the pressure of the air according to variations in such air pressure due to changes in conditions of the molten metal.

Another and more specific object is to provide means and method of the character indicated, for maintaining a constant volumetric flow of air for maintaining a constant rate of pouring.

Another object of the invention is to provide means and method of the foregoing character which includes a pouring tank and a mold above the tank, in which air pressure is developed in the tank for forcing the molten metal into the mold, which includes a novel control arrangement for rapidly pouring the metal from the tank to the mold cavity, and thereafter reducing the rate of pouring in that portion of the operation in which the mold cavity is filled.

Other objects and advantages of the invention will appear from the following detailed description taken in conjunction with the accompanying drawings in which:

The single figure shows a pouring tank, ladle, and mold assembly in vertical section, and control means therefor indicated diagrammatically.

Referring now in detail to the drawings, a pouring tank is indicated at 10 which includes a receptacle 12 having a removable sealed cover 14. The cover may be held on the receptacle by any suitable clamping means indicated semidiagrammatically at 16. The tank thus becomes sealed for maintaining air pressure therein in the manner described in detail hereinbelow, the air being introduced into the tank through conduit means 18.

In the tank is a ladle 20 for containing molten metal 22. The ladle may be of any suitable kind, and after being filled is placed in the tank by suitable means, after which 3,425,483 Patented Feb. 4, 1969 the cover 14 is applied to the tank and secured thereto in sealing relation. A pouring tube 24 is mounted on the cover 14, and when the cover is in place on the receptacle, it extends downwardly to a point closely adjacent the bottom of the ladle. The pouring tube may be mounted in sealed relation in the cover 14 by any suitable means, and terminates upwardly in an adapter 26 on which a mold 28 is placed. The mold 28 for present purposes may be a conventional mold having a cavity 30. A stopper 32 of graphite is incorporated in the mold, having a head 34 en gageable with a seat 36 in the mold surrounding a passage 38 leading from the pouring tube to the cavity. The stopper 32 is normally in lowered position for closing the seat 36 and passage 38, but is raised to permit the molten metal to pass into the cavity. This stopper in its movement is utilized for actuating controlled instruments suchas switches in the control apparatus to be described in detail hereinbelow.

Briefly stated, the casting operation is accomplished by producing air pressure in the tank which, acting on the exposed surface of the molten metal in the ladle, forces it downwardly and then upwardly through the pouring tube 24 and the passage 38 into the cavity of the mold. The mold, as will be understood, is detachably mounted on the tank, and after the mold cavity is thus filled, the stopper 32 is lowered to close the cavity, and upon release of the pressure in the tank, the molten metal in the passage 38 recedes and flows down through the pouring tube to the normal level in the ladle. The mold is then removed, and another empty mold is placed in position and the operation is repeated.

Referring now to the control arrangement shown at the left hand portion of the figure of the drawings, this apparatus includes means for maintaining a constant volumetric flow of air into the tank for thereby producing a constant rate of flow of the molten metal. Maintaining a constant volumetric flow of air involves sensing of the air pressure in the system and increasing the effective pressure forcing the air into the tank to compensate for increase in back pressure therein which in turn is caused by such factors as increase in viscosity, increase in head of the molten metal in the pouring tank-mold apparatus. The conduit 18 is connected with any suitable source for developing air pressure (not shown) such as a pump. Interposed in this conduit is a flow meter 40 of known kind, which includes an orifice 42 disposed in the conduit constricting the flow of gas and producing a differential in air pressure above and .below it. The air pressure in the conduit 18 is sensed at points respectively upstream and downstream from the orifice 42, represented diagrammatically by flanges 43 and 45, and means controlled by differential in pressure at those points is provided for maintaining constant volumetric air flow through the conduit, as described below.

The conduit 18 divides at 44 and continues through two branches, 46 and 48, for enabling respectively greater and lesser amounts of air to flow through the conduit. These branches rejoin at 50, and the path of the air flow continues through the main \conduit into the pouring tank. A normally closed diaphragm throttling valve 52 is interposed in the branch 46, while a normally closed similar valve 54 is interposed in the conduit-48. These valves, of known type, are opened upon development of predetermined pressures in the corresponding diaphragm housings in the manner described below.

An on-oif, normally closed, diaphragm valve 56 is interposed in the conduit 18 downstream from the branches 46 and 48. A branch conduit 58 leads from the conduit 18 downstream from the valve 56, in which is another diaphragm-operated normally open valve 60, which when open enables the air to be exhausted from the tank, the branch 58 leading to atmosphere. In the casting operation, the valve 60 is closed for enabling development of the desired air pressure in the tank.

The controls referred to above include two flow controllers 62 and 64 having respectively different controlling characteristics. One of these controllers, e.g. 62, controls the desired rapid flow of air referred to above, in which the molten metal is forced through the pouring tube to the mold cavity; the other controller 64 then controls the How of metal at a lower rate in the step of actually filling the mold cavity. The invention is not limited to two such controllers and corresponding rates of control, but is sufliciently broad to include only a single rate of flow as, for example, when it is not desired to utilize two different rates of pouring in a casting operation. The concept of the invention is providing means and method which, by sensing air pressure, produce a constant volumetric air flow.

The controllers 62 and 64, of known kind, are connected with the air conduit 18 through conduits 66 and 68 which communicate directly with the conduit 18 at the points referred to, respectively upstream and downstream from the orifice 42. The flow meter 40 includes conventional means, such as the flanges 43 and 45 with connections therein for connecting the conduits 66 and 68 to the conduit 18 at the points mentioned. The details of the connections of the controller to the conduit 18 need not be entered into here. It is deemed sufficient to state that this feature is of known characteristics, and by providing the proper connections, the differential in those portions of the conduit operate the controller 62. The controller 62 is manually set to provide the desired establishment and shut-off of the air flow at predetermined pressures in that air flow. The controller 62 includes a conduit 72 leading to the diaphragm valve 52, and upon the development of increased back pressure in the tank, the controller serves to further open the valve 52.

The back pressure in the tank is transmitted through the conduit 18 to the metering orifice 42, and as a consequence the difierential of the pressure above and below the orifice is reduced. This reduction in differential pressure operates through the conduits 66 and 68 to control the controller 62 to further open the valve and enable increased flow of air. The back pressure may be caused by increased viscosity of the molten metal, as stated above, requiring greater pressure for maintaining a constant rate of pouring.

The controller 62 and 64 by their inherent characteristics integrate the factors, such as variation pressure and temperature, affecting air flow so as to produce constant volumetric air flow. The constantly increasing volumetric increments of air transmitted to the tank produce displacement of corresponding increments of molten metal into the mold.

Associated with the controller 62 is a solenoid operated switching valve means 74, including a valve 76 and a solenoid 78. The valve includes a two-way arrangement which, in one position, connects the controller 62 with a supply of compressed air through conduits 80, 82 and 84 for operating the valve 52. The supply of compressed air may be the same as that providing air in the conduit 18, or other source. When the valve 76 is in the one position mentioned, and the conduits 80 and 82 are connected, the air pressure provided is transmitted through the controller and the conduit 72 to the valve 52 for opening, or further opening, the latter in the manner stated. When the valve 76 is in its opposite position, it provides a shunt circuit to the controller 62 through conduits 72, 86 and 80, to balance the controller.

The controller 64 may be a duplicate of the controller 62, and is set for controlling the valve 54 for producing a lesser flow of air than through the valve 52. A solenoid operated valve means 88 is provided in connection with the controller 64. Also, a shunt circuit line 89 is provided, and another conduit 90 leads from the valve means 88 to the conduit 84,

' Other instrumentalities may be incorporated in the apparatus, such as a flow recorder 92, for recording the differential of the air pressure above and below the orifice 42. Similarly, a pressure gauge 94 and a pressure recorder 96 may be connected to the conduit 18 at a point adjacent the tank to indicate and record the pressure in the tank. The instruments 92, 94 and 96 are incorporated here for convenience and do not as such enter into the concept of the present invention.

In the casting operation, the initial steps taken may be manual, as for example turning on the main air supply. The stopper 32 in the mold is lowered to closed position, and this movement of the stopper may be utilized for controlling certain of the apparatus. When the stopper is lowered, it controls the two-way valve 98, which is similar to the valves 74 and 88, for opening the valve 56 and closing the exhaust valve 60. The solenoid of the valve 98 is controlled by a switch operated by the stopper. This may also control the solenoid 78 and actuate the valve 76 to connect the controller 62 with the air supply. The air then flows through the conduit 18 which includes the branch 46 which is open through the valve 52 at this stage.

The air flows into the tank 10 at a relatively rapid rate, as determined by the valve 52. The molten metal rises in the pouring tube 24 and the passage 38 in the mold. The molten metal on engaging the stopper head 34, raises the stopper and actuates switch means for de-energizing the solenoid 78 and energizing the solenoid of the valve means 88 associated with the controller 64. De-energization of the solenoid 78 enables the valve 52 to close, and energization of the solenoid in the valve means 88 actuates that valve means and causes opening of the valve 54. Since the valve 54 is of lesser capacity than the valve 52, the pouring operation continues at a reduced rate until the mold cavity 30 is filled. The stopper, upon rising, may actuate another switch which deenergizes the solenoid of the valve means 88, enabling the valve 54 to close. When the cavity is filled, the stopper is lowered to close the seat 36, and this movement controls the valve 98 to shut oif the valve 56 and open the exhaust valve 60. A time delay is interposed between the shutting of the stopper and actuation of the valve 98, to produce a delay of approximately one second.

While I have disclosed herein a preferred form of the invention, it will be understood that changes may be made therein within the scope of the appended claims.

I claim:

1. Pressure casting and control apparatus therefor, comprising a pressure tank adapted for placement therein of a ladle having molten metal, a pouring tube associated therewith and adapted for placement of a mold thereon with a bottom passage communicating with the pouring tube, an air conduit leading to said pressure tank, means for forcing air through said conduit and thereby producing air pressure in said tank, means forming a metering orifice in said air conduit, controller means for sensing air pressure difierential on opposite sides of said orifice, valve means in said air conduit, and means controlled by said controller in response to sensing of the differential in air pressure on opposite sides of said orifice for controlling said valve means and maintaining a predetermined rate of flow of air into said tank.

2. Apparatus according to claim 1 wherein the last named means controlled by said controller is operative for maintaining a constant volumetric rate of flow of air into said tank.

3. Apparatus according to claim 1 in which said controller is operative for increasingly opening said valve means in response to decrease in said differential in air pressure.

4. Apparatus according to claim 3 in which said valve means is downstream from said orifice.

5. Apparatus according to claim 1 in which sut-olf valve means and exhaust valve means are provided in said air conduit, and means is provided operative in response to molten metal rising to a predetermined height in said mold for closing said shut-off valve and opening said exhaust valve for opening said tank to atmosphere.

6. Apparatus according to claim .1 in conjunction with a second controller operative for enabling passage of air through said air conduit into said tank at a rate different from that controlled by the first controller.

7. Apparatus according to claim 6 in which the first controlled enables passage of air at a faster rate than the second controller, and including means for rendering operative the first controller for pouring at a fast rate, and means responsive to molten metal reaching a predetermined height in the pouring tube and mold for ren- References Cited UNITED STATES PATENTS 8/1952 Sylvester 164-119 7/1961 Hursen 164155 J. SPENCER OVERHOLSER, Primary Examiner.

R. SPENCER ANNEAR, Assistant Examiner.

US. Cl. X.R. 164-4 

